1. Field of the Invention
The present invention relates generally to electronic access control systems actuated by coded input and more particularly to a code type electronic access control system adapted for mounting in conventional wall switch boxes provided with standard toggle type switch plate closures.
2. Description of the Prior Art
The use and construction of electronic combination locks for securing various closure means such as residence and business premise doors, garage and vehicle doors and for the operation of other access control and securing means are well known in the art. Such code type acces control devices usually employ a plurality of push-button input switches. These switches when operated in a predetermined code sequence or combination may activate circuits to arm or disarm a security system. Alternatively, such devices may operate a solenoid or similar device to move or release a bolt or other means to lock or unlock a security device or closure. Alternatively, an electronic combination lock may be operated or triggered by actuation of a single push-button switch in a timed predetermined sequence.
The following patents are illustrative of prior art technology in this general area.
U.S. Pat. No. 3,633,167 to R. A. Hedin (1972) PA1 U.S. Pat. No. 3,772,574 to D. C. Hughes (1973) PA1 U.S. Pat. No. 4,197,524 to R. J. Salem (1980) PA1 U.S. Pat. No. 4,408,251 to I. M. Kaplan (1983) PA1 U.S. Pat. No. 4,425,597 to W. E. Schramm (1984) PA1 U.S. Pat. No. 4,455,588 to H. Mochida (1984) PA1 (a) difficulty in finding or identifying the disarming means, PA1 (b) difficulty in activating the disarming means, and PA1 (c) time allowed for disarming, can be optimized so that general security is enhanced and other factors optimized also.
U.S. Pat. No. 3,633,167 to R. A. Hedin discloses a push-button security control system using solid-state components for generation of a preselected combination of coded signals upon operation of push button means and includes both a timing circuit to assure the correct code signal is generated within a predetermined interval and means to allow ready alteration of the preselected code.
U.S. Pat. No. 3,772,574 to Hughes discloses an electronic combination lock that uses a plurality of logic functions requiring the input of a predetermined number of pulses to a counter means for opening a lock.
U.S. Pat. No. 4,197,524 to Salem discloses an electronic combination lock activated by a series of sequential taps upon a surface such as a wall in a predetermined interval pattern. The apparatus compares the pattern of taps received with a predetermined pattern and operates a lock only if the two patterns conform.
U.S. Pat. No. 4,408,251 to Kaplan discloses a push-button type security system in which either a plurality of push buttons are operated in a predetermined sequence or a single push button is operated in a coded sequence. The coded signals are directed over a minimum of conductors to a security system within a secure area such as within a garage at a location removed from the access door.
U.S. Pat. No. 4,425,597 to Schramm discloses an electronic combination lock designed for use in automobiles and operated by sequential pulses directed from two activator means such as push buttons or the like.
U.S. Pat. No. 4,445,588 to Mochida et al discloses an electronic push-button lock operated with a single push button which may be activated in a sequential code pattern in the form of a tune or melody.
Although the above and other devices have been used and in some cases have achieved widespread use, they have been subjected to several serious drawbacks and disadvantages.
On of such disadvantages is the necessity of providing special mounting and protective means for such electronic locking systems. A further disadvantage is that most combination type electronic locks use a plurality of push buttons for encoding and consequently require a relatively large mounting and containment means. These disadvantages not only increase the cost of such electronic systems, but make them conspicuous so that some of the advantages of the coded lock are lost.
Multiple push-button electronic combination locks are also subject to decipherment of the combination by close observation and by so-called "dusting". In "dusting" the push buttons are dusted by unauthorized persons with a chemical compound prior to operation of the push-button panel in the correct combination by an authorized person desiring to gain access to a secure area. The push buttons may subsequently be examined by the unauthorized person, i.e. the duster, and by a simple chemical analysis the particular buttons which have been activated are easily identified. While the sequence of operation of such buttons is not revealed by dusting, identification of the activated buttons serves to substantially reduce the number of possible operational combinations to a number small enough to enable solution and detection of the correct combination within a relatively short period, thus seriously compromising the security of the locking system.
While various types of combination locks have, furthermore, been devised with only one or two sequentially operated code buttons, as illustrated by the Kaplan and Schramm patents mentioned above, which avoid the difficulty of "dusting", such sequential time coded systems have not provided a complete solution of the above encountered problems and have been subject to other disadvantages.
Further disadvantages of many such prior art devices is the necessity of drilling special holes or openings in conspicuous places to accommodate the push-button switch mechanism. Prior locking systems, furthermore, have not been easily mounted in locations where space is at a premium such as, for example, locations on door jambs and the like between large glass or other panels. Such environments may be found, for example, on glass store fronts and the like where only relatively narrow jambs and moldings are positioned between large glass expanses.
As pointed out above prior devices have tended to be conspicuous so far as their security functions are concerned, thus drawing the attention and interest of unauthorized persons. For example, the display of a multi-push-button panel at or near a closure means such as a door is more than likely to arouse the interest of unauthorized persons in such closure and the reaso for the use of extraordinary protective measures to maintain the security of such closure. The security system itself may thus tend to increase attempts to breach security. The conspicuousness of a code panel is of particular importance when such panel is used as a disarming device as will presently be explained.
While the fewer code buttons that are used, the smaller the overall size of the push-button panel, and the less conspicuous it will be, even those panels making use of only two sequentially operated code buttons have required specialized mounting means and have tended to be fairly conspicuous. Furthermore, arrangements such as disclosed in U.S. Pat. No. 4,197,524, which have required no switch panel at all, have been expensive to implement and are not usable in all locations since the surface to be tapped must be of such character as to readily transmit distinct shock impulses. Furthermore, a fairly vigorous tap is necessary to activate the code system, else such system will be too easily activated and will be interfered with by noise and other disturbances in the environment. Moreover, the imposition of fairly heavy tapping on the surface is subject to both visual and aural observation or detection which may result in inadvertent transfer of the code to unauthorized persons. The surface must also, of course, tend to damp continuing vibrations rather than be subject to large continuing secondary and harmonic vibrations which could interfere with detection of the primary code impulses.
There has consequently been a need for a relatively simple, compact and self contained code type locking/unlocking system that may be easily mounted in either existing mounting receptacles such as light switch receptacles and the like or alternatively may be easily contained and mounted in conventional light type switch receptacles without the use of special or auxiliary mounting means.
There has been a particular need for a simple, economical and inconspicuous access control device for arming and disarming various types of security systems in secure areas in households, offices and government installations. In such environments a master security control panel is usually provided in a secure location within the secured premises and is customarily locked against tampering. The security system may typically include audible or visual alarm means activated by detection of the presence of an intruder or unauthorized person within such premises. Such alarm may be activated in any known fashion, for example, by heat or infrared detection of the presence of a living body, or by the detection of sound, movement, interruption of light beams and by the use of other physical principles. Upon the detection of signals indicating the apparent presence of an intruder, an alarm circuit is activated by the security system and an alarm set off either audible on the premises, or visual or audible at some other location such as a security station manned by security personnel or at a central police station or the like.
Typically there is a predetermined time delay from first detection of the presence of an apparent intruder to the instigation of an alarm in order to provide time for authorized persons to identify themselves to the security system or to otherwise deactivate the system. Typically in a residence or business, for example, there will be a 40 to 50 second time delay for a person entering the premises to activate a means to disarm the alarm system. For example, in a residence, switch means will be located inside but adjacent to the entrance, that is within an alarm zone. Such switch means is activated by the residents to turn on, or arm, the alarm system before leaving and is again activated by the residents to turn off, or disarm, the system upon reentering the premises. The amount of time provided to disarm the system is dependent essentially upon the degree of difficulty of the actual disarming operation, which operation can be divided into two periods. The first of such periods is the time taken to locate the disarming means and the second of such periods is the time required by both an authorized person and an unauthorized person to correctly actuate the disarming mechanism or means. If it is both difficult to find the disarming means and difficult to activate it, a significantly greater time can be allowed for disarming than if only one such difficulty is present. A longer time period is advantageous for activation by authorized persons, since such longer period diminishes the possibility of mistakes resulting in accidental activation of the alarm. A shorter period on the other hand increases the security of the system. Thus increasing difficulty in finding and disarming the securing disarming means significantly increases the overall security of the system. It is advantageous, therefore, if a disarming device is difficult of access for unauthorized persons, but easy of access for authorized persons, i.e. because such persons know where it is. This will inherently provide the authorized person with additional time to activate the disarming device in the correct manner, thus diminishing possible errors. It is also advantageous if a finite time is available to input a correct code sequence so an unauthorized person is under a further time constraint to correctly operate the code device.
It will be seen, therefore, that a security system may be secure in proportion to several interrelated factors (a) the time required for operation must be limited to interfere with decoding or tampering by unauthorized persons, but not so limited as to deny authorized persons a reasonable time to operate the system, (b) the difficulty of operation must be compatible with the time available, the sophistication and patience of the authorized persons who will be using the system and the cost benefits of the security measures to be taken. It is advantageous usually to increase the difficulty of identifying the disarming means in order to allow as much time as possible, consistent with security, to correctly activate such disarming means.
Unfortunately, in former alarm systems it has seldom been possible to maintain the basic factors of security for disarming systems at their maximum effectiveness. Thus, if an uncomplicated disarming mechanism is used, it may be made more difficult to identify or locate, while keeping the activation time low. On the other hand, if a more sophisticated or complicated security activation arrangement is used, it is usually more difficult to conceal except by providing false concealment such as hidden closure means and the like, for example, a false panel behind which a key or multicontact code panel is concealed.
Unfortunately, the provision of such arrangements as hidden panels and the like to increase the time likely to be necessary for an intruder to find or identify the disarming means also requires provision of more delay time for authorized person to reach and deactivate the disarming means.
There has, therefore, been a need for a code type security control or access control device which is particularly applicable to use for disarming a security system which optimizes interrelation of the various factors contributing to effective security of such systems.
There also has been a need for a code type locking/unlocking system which after mounting is inconspicuous yet easily operated and at the same time secure.
There has further been a need for a locking/unlocking system which is economical and simple to install and can be installed in standard wall type receptacles with a minimum of specialized tools or mounting means.